Setting up iMC784 for a proper PQ monitoring
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Transcript of Setting up iMC784 for a proper PQ monitoring
Understanding the need for a proper
PQ set-up
Connecting iMC784
White paper I 02
Power Quality Analysers represent one of the most advanced metering
equipment, which became an essential part of every modern utility, industrial
and even building installation. Power quality related issues are a disease of a
modern supply system and are mostly hard to locate. They are very often
confused with equipment malfunction. Lack of information about supplied
power quality can lead to unexplained production problems and malfunction or
even damage to equipment used in production process.
Conventional meters were not designed to detect such anomalies hence PQ
analysers were built. As every musical instrument need to be tuned so must be PQ
analyser properly set-up and positioned on a right place to perform its task.
Besides installation place it is also important to understand what kind of loads
are installed on monitored location and what are normal operation
consumption levels.
PQ analyser iMC784 can be connected to any voltage level by means of dedicated
CTs and VTs. Choosing proper secondary values is important to be able to detect
various events with higher amplitudes. iMC784 can accurately measure currents
up to 15A and phase voltages up to 600V, which gives margin on three times
nominal value for 5A / 230V and much more when secondary values are 1A nad
110V.
For proper PQ analysis it is advised that connection system is three-phase four-
wire in order to monitor all phases directly and to detecet anomalies that would
occur in any power line. When this is not possible iMC784 supports all other
standard connection systems.
“iMC784 PQ analyser is
normally set up by a
Setting & Monitoring
software MiQen.
MiQen is user friendly
and powerfull tool
comes free as a part of a
iMC784 PQ monitoring
package.”
The iMC784 can be part
of a complete system by
using the server SW -
MiSMART
Installation usually requires access to the restricted places and during
installation power is usually cut off. Therefore any further post-installation
intervention is not wanted. Therefore in case of wrong connection or project
change it is possible to remotely change phase channels through communication
and setting software.
PQ analyser iMC784 is by default already set up for PQ monitoring on four wire,
low voltage 230V, 50Hz system. When it is installed in a different system, certain
parameters should be modified.
White paper I 03
Enabling PQ monitoring“Settings can be also
performed offline by
MiQen setting software
and uploaded as a
complete setting file
(*.msf f i le) or just
individual section (e.g.
communication, energy,
I/Os, Alarms, Recorders,
Power Quality...).“
“ N e u t r a l l i n e C T
transformation ratio
can be separately
defined since currents
t h a t a r e f l o w i n g
through neutral line
have usually lower
magnitude”
„ I f m o re i d e n t i c a l
analysers should be
installed, setting file can
be uploaded to all and
save overall installation
time.”
White paper I 04
Monitoring mode can be set to standard EN50160 or can be disabled.
Electro Energetic System can be set to one of the systems defined by
EN50160
Monitoring voltage connection corresponds to connection system
(three or four wire)
Operating supply voltage is always a secondary voltage of a VT. This is a
nominal voltage for PQ analysis. If connection system is three phase,
phase-to-phase voltage needs to entered
Nominal power frequency can be either 50 Hz or 60 Hz
Flicker calculation function is different for systems with 110V or 230V
nominal low voltage. For proper flicker evaluation this needs to be chosen
correctly
Monitoring period is defined by EN50160 as 1 week
Flagged deviation evaluation; in some cases certain variation or
anomaly in supplied power triggers also some other events (e.g. certain
harmonics can also trigger flicker). Instrument detects this collateral event
and marks it (assigns a flag). PQ recorder always stores all events. But for
PQ report, user can define weather to include all events or should it skip
flagged events, which contribute to worse overall PQ report.
All Monitored data is stored in internal flash memory and evaluated
within the instrument itself. Optionally it can also be sent into the
MiSMART system server for remore monitoring
Settings of individual PQ indices (frequency variations, voltage variations...) are
predefined according to EN50160 requirements. It is always possible to change
them. In this case, report will not be a EN50160 compliant report (notice within
report).
Beside voltage and frequency related variations and events, latest standard for
class A PQ analysers (IEC61000-4-30 Ed.3) also defines procedures for current
monitoring. iMC784 is built according to latest standard and enables monitoring
current related disturbances.
Described settings are required for PQ monitoring. Advanced operation of
iMC784 enables also PQ analysis with precise event detection and recording in
order to evaluate cause and origin of an event.
“Comparing voltage and
c u r r e n t r e l a t e d
d i s t u r b a n c e s h e l p s
distinguish between
disturbances coming
f rom the gr id and
disturbances generated
by installed equipment
(production processes,
generators…)”
White paper I 05
The iMC784 instrument can be configured to be part of a comprehensive PQ
monitoring system where instrument-evaluated data is sent into the MiSMART
system SW to transfer PQ data automatically (via autonomous push XML
communication) as well as on demand data (via FTP) from one or multiple
instruments.
“Viewing PQ data as an
aggregated table with
the MiSMART native web
client"
White paper I 06
Additional PQ record settings
This detailed analysis is a useful tool for preventing further occurrence of events
and proper network planning. For such analysis, it is crucial to define various
triggers and signal records that will help evaluate the cause, nature, duration and
area spread of the event.
Setting up triggers for various event detection is simple by using MiQen setting
software:
White paper I 07
For each event detection (trigger) it is possible to define various actions:
- Waveform records on chosen channels (4 current, 4 voltage and 8 digital)
- Disturbance record (RMS reading with half cycle resolution) on chosen
channel
- Send crosstrigger to up to eight other PQ analysers
Also important is data format of recorded signals so they can be imported,
visualized and analysed with various softwares. For this purpose iMC784
supports standard PQDiff and Comtrade data formats.
“Signal shape and RMS
values records can
consume vast amount
of internal memory if
n o t c o n f i g u r e d
correctly.”
Transient triggers can detect voltage and current impulsive and
oscillatory transients with 32 µs resolution. This type of triggers are used
for shortest duration time events detection.
PQ Event triggers are defined with PQ standards. PQ events, which are
already part of standard PQ monitoring and reporting can be assigned
here for more detailed analysis by recording signal shapes.
External triggers are used in larger systems or in combination with
other equipment (e.g. protection relays). PQ analyser sends Ethernet
trigger (cross trigger), when it detects event, to other PQ analysers in the
network in order to evaluate area spread of an event. This is possible by
simultaneous records of the same event on different places. Information
is not lost due to pre-trigger time and precisely synchronised internal
clock. Digital triggers are extension of triggering mechanism to triggers
detected by other equipment or process and sent to PQ analyser in a
form of a digital signal.
Combined triggers are used for selective triggering mechanism. This
function enables generation of triggers as a logical combination of other
triggers, digital signals and alarms. By masking certain trigger
conditions this function helps detect events more precisely.
White paper I 08
Waveform recorder is used for most detailed analysis of detected event
with up to 625 samples/cycle and up to 0.5 sec pre-trigger time.
Disturbance recorder is used for longer period transition event analysis
but with lower resolution. Half-cycle or one-cycle resolution and up to
30sec pre-trigger time.
PQ recorder is permanent recorder (when enabled) and records all PQ
related variation and events as described in EN50160 standard with
aggregation intervals as described in IEC61000-4-30 standard.
Fast trend recorders are user defined recorders of all measured
quantities, with down to 1 sec storage interval.